The Enterprise follows unusual readings to an unexplored planet and is hit by waves of turbulence. Spock identifies the waves as ripples in time. Sulu’s panels short circuits and he’s badly injured. McCoy comes to the bridge and risks using a few drops of cordrazine despite the risks. Sulu recovers as one last time ripple arrives. When it strikes, McCoy accidentally injects himself with a full hypo of cordrazine. He goes berserk, accusing the crew of trying to kill him. He runs off of the bridge and security teams mobilize to try and capture him. McCoy makes his way to the tranporter room, knocks out the attendant, and beams down to the planet.
Spock warns that cordrazine overdoses induces paranoia and hysteria. They receive word that McCoy has used the transporter to beam into the center of the temporal disturbance. Kirk assembles a landing party and they beam down to the planet’s surface in the midst of a vast ruined city. As they search for McCoy, Spock determines that a single torus-shaped object is the source of the time ripples. When Kirk states a question, the object responds, identifying itself as the Guardian of Forever. It describes itself as neither machine nor organic, and both, and a functioning time portal. It shows them Earth’s history, but Kirk and Spock are distracted when McCoy comes running up. They restrain him and Kirk suggests they use the portal to go back and relive the accident, avoiding the hypo incident. The Guardian informs them it can’t slow the accelerated rate of display that it is offering them. As Spock start taping the Guardian’s playback, McCoy recovers and leaps through the portal. Uhura tries to contact the Enterprise but gets no response. The Guardian informs them that the Enterprise, and everything that they’ve ever known, is gone. McCoy has somehow changed history, stranding them with no past and no future.
The landing party has the Guardian replay history again and Kirk and Spock prepare to go through to set right whatever McCoy altered. Using his tricorder recording, Spock pinpoints the time to jump within a week. Kirk advises the others to try if they don’t come back. Kirk and Spock pass through and find themselves on a New York City street in 1930. Their unusual clothing begins to draw clothing and Kirk steals clothing from a nearby fire escape. A police officer notices and Kirk tries to explain that Spock is Chinese and fell into a mechanical rice-picker. The police officer doesn’t believe them so Spock renders him unconscious and they flee to a nearby basement. They don the clothing and Spock speculates that they’ve arrived approximately a week before McCoy, and that the current of time will bring him to the same spot.
The owner of the mission they’ve taken refuge in, Edith Keeler, comes downstairs and demands to know who they are. Kirk eventually tells them a policeman was chasing them after they stole the clothing. She offers them a job and Spock, needing the money to pay for components to scan the tricorder database, accepts.
Later, the men in the mission gather for supper and Edith gives a speech about the glories of the future, including nuclear power and space travel. Kirk is impressed. Later, Keeler congratulates them on their job cleaning the basement and Edith sets him up at a vacant apartment in the building where she lives. Once they move in, Spock uses 1930s components to assemble a crude computer but warns that he’ll be lucky to succeed within a month. Edith arrives with a job offer and notices the strange equipment.
Later, as they work at the mission, Spock notices another mission employee using precision tools that he needs. They steal the equipment and later, Edith confronts them about the theft. Spock says he would have returned them and Kirk assures Edith he’s telling the truth. Edith agrees to drop the matter as long as Kirk walks her home and answers a few questions. As they walk home, Kirk speaks of the future and Edith assumes he’s making things up.
Spock briefly accesses a newspaper article featuring Edith’s obituary. Kirk arrives and Spock warns that the news he’s discovered may be distressing. Spock plays back an article from six years from now, stating that Edith meets with President Roosevelt. The circuits burn out before they can read more, but Spock informs him that he saw Edith’s obituary stating she dies in a traffic accident. Edith is the focal point: however, they don’t know which future is the correct one. They’re left to wonder if McCoy kills her or prevents her from being killed. Kirk orders Spock to repair the circuits, but Spock warns that they may have to kill Edith to set things straight.
A ranting McCoy arrives on a street in New York at night. He spots a drunk and demands answers. He grabs the man and notices that he’s wearing primitive clothing, and thinks “they” are trying to trick him. McCoy collapses and the drunk takes his stolen phaser, and then inadvertently activates the disintegration setting, destroying himself and the weapon.
The next morning, a much calmer McCoy staggers into the mission and Edith takes him into the back to a spare cot, as Spock arrives unaware of his comrade’s presence. Later, he manages to access the records and determine that Edith survived a street accident, and then inspired a pacifist movement that delayed America’s entry into World War II. The Nazis developed nuclear weaponry and won the war. Spock is unable to determine the exact time or method of her death. Kirk admits that he’s fallen in love with Edith but Spock warns that she must die.
Edith tends to the weakened McCoy in the back. He talks vaguely of the future and she notes that he speaks similarly to her friend. McCoy, his memories coming back, identifies himself as a Starfleet officer but she assumes he’s demented.
Later, Kirk talks to Edith on the stairs and she trips and almost falls. Kirk catches her as Spock looks on. The couple kiss and Edith leaves, and Spock notes that the incident may have been when she died. Kirk notes that McCoy isn’t there yet but Spock warns they are not sure what will happen. He notes that if Kirk does what his heart dictates, millions will die who didn’t die before.
Edith visits McCoy, who is in much better shape but believes his current location is another hallucination. He thanks her for her help and he offers to work in return for her aid. When she mentions that her friend will be taking her to a Clark Gable movie, he doesn’t recognize the name.
A bit later, Kirk escorts Edith across the street from the mission to a movie. When she mentions Clark Gable, he doesn’t recognize the name and she comments that McCoy said the same thing. He runs back to the mission just as Spock and then McCoy emerge. The three friends are reunited and a distracted Edith starts to cross the street. Kirk goes to stop her but Spock warns him not to. McCoy tries to save her and Kirk is forced to stop him. Edith is hit by a truck and dies in the street, while McCoy wonders if Kirk knows what he’s done. Spock assures the doctor that Kirk knows all too well.
The three officers return to the present through the Guardian, only a few seconds after they departed. The Guardian assures them that time has been restored, and offers to act as their gateway to other such journeys. A contemplative Kirk says to “get the hell out of here” and they depart. Share this article with your friends